Phytotoxicity of chlorinated aliphatics to hybrid poplar (Populus deltoides x nigra DN34)

Effects of a series of chlorinated ethenes and ethanes on hybrid poplar (Po pulus deltoides x nigra DN34) were assessed in laboratory experiments. Popl ar cuttings were grown in sealed reactors with hydroponic solutions and wer e exposed to a chlorinated solvent for a period of two weeks. Exposure conc entrations ranged from 0 to 0.4 mM for perchloroethylene to 0 to 8.4 mM for 1,1-dichloroethane. Effects were assessed by gravimetrically monitoring tr anspiration and measuring change in cutting mass. The zero-growth concentra tions of the chemicals tested were 0.3 mM perchloroethylene, 0.9 mM trichlo roethylene, 0.9 mM 1,1,2,2-tetrachloroethane, 2.0 mM 1,1,1-trichloroethane, 2.3 mM 1,1,2-trichloroethane, 4.8 mM trans-dichloroethylene, 5.6 mM 1,1-di chloroethylene, 6.0 mM cis-dichloroethylene, and 10.7 mM 1,1-dichloroethane . Adverse effects were found to increase with increasing number of chlorine atoms within a homologous series of ethenes or ethanes. Ethenes were more toxic than similarly chlorinated ethanes.